The present invention relates to a power window apparatus, for use with a motor vehicle, for driving a window glass for opening and closing the window with a motor, for example. More particularly, the invention relates to a power window apparatus with a safety device which performs a safety control operation when the hand, neck, etc., of a driver or passenger is interposed between the window glass and the sash.
Generally, a power window apparatus is constructed so as to drive the window glass for opening and closing purposes with a drive source, for example, an electric motor. In the power window apparatus of this type, the window glass is automatically moved for opening and closing by the drive source.
In such a power window apparatus, to cope with the situation where the hand or neck of a passenger is accidentally interposed between the window and the sash, a safety device is provided. The safety device operates such that, when it detects a state where an object is interposed between the window glass and the sash, movement of the window glass is stopped, or the window glass is forcibly moved in the opening direction.
To detect the state where an object is caught in the window, the safety device measures the rotational speed of the motor, which is proportional to the opening and closing speed of the window glass, since when the load on the motor for moving the window glass increases, the motor speed decreases. Specifically, the safety device detects when the motor speed drops below a preset value, i.e., a state which corresponds to a load indicative of the hand, neck, etc., of the driver or passenger being caught in the window.
When the window is fully closed to hit the sash, its speed is reduced to zero. The conventional detecting system mentioned above sometimes mistakenly recognizes this speed reduction as an object-caught state. As a result, the safety control operation starts to fully open the window, and the window is left open.
To avoid the window being left open, the current position of the window can be constantly monitored utilizing the quantity of rotation of the motor. When the window approaches the position where it is fully closed, the safety control mode is disabled, allowing the window to be fully closed. That is, a safety control mode disabling region is provided. The safety control mode disabling region must cover a very small distance in order to prevent fingers of children from being caught in the window. For this purpose, the position for safety control mode disabling is typically set at a position approximately 4 mm short of the position where the window is completely closed.
Further, in the above-described detecting method, if the reference value of the object-caught detector is set at a critical value, the following problem arises. In a region just before the window is completely closed and the window glass is in contact with the weather strip of the sash, the frictional resistance between the window glass and the weather strip impedes the rotation of the motor to reduce the motor speed. The object-caught detector can mistakenly recognize this state as that in which an object is caught in the window. As a result, the closing operation of the window is stopped, so that the window is incompletely closed.
In a window using the weather strip WS having the structure in cross section as shown in FIG. 15, the upper edge of the window glass 207 comes into contact with the lip WL of the weather strip WS at a position approximately 15 mm short of the position where the window is completely closed. In the region where the window glass comes in contact with the lip (referred to as a run channel region), the closing operation of the window is impeded, so that the motor speed decreases. In this state, erroneous detection tends to occur. To avoid such erroneous detection, the reference value for the object-caught detection must have some range of variation in value. However, if the reference value is so set, the sensitivity of the object-caught detector when it detects an object being caught in the channel region is reduced. Accordingly, it is difficult for the object-caught detector to detect a state, for example, where a finger is caught in the window. In the figure, SS designates a sash.
The actual power window apparatus employs a gear mechanism, wire, and pulley mechanism for transferring the rotational force of the motor to the window glass. Accordingly, the power window apparatus inevitably suffers from problems such as variations in the rotational amount of the motor owing to the damper effect caused by the presence of the gear mechanism, stretching of the wire, wear of the pulleys, and the like. As a result, a precise relationship between the number of revolutions of the motor and the position of the window cannot be maintained over time, thus making it difficult to accurately control the safety mode disabling region to within that distance.
Thus, the conventional power window apparatus with a safety device cannot simultaneously satisfy both contradictory requirements of detecting an object being caught with a high sensitivity particularly in the run channel region and preventing erroneous operations when the safety control operation is carried out and the window is completely closed.